Closed caption decoders decode closed caption data embedded in television signals and display in real time the closed caption text with the associated video image. The closed caption decoder may be a stand alone box or integral with a television. The caption text displayed on the screen of the television allows hearing-impaired persons to read the text of the audio while watching television.
Closed caption systems provide less benefit to persons having a limited vocabulary in the language of text, such as persons with English as a second language, because the displayed text may contain words that the viewer may not understand. Such persons using the closed caption system, upon the occurrence of an unknown word, may either skip the unknown word, or write down the word and look it up in a dictionary. For the latter approach, writing the word correctly after seeing the word a short time may be difficult. Also looking up the word in a dictionary is time consuming.